The way they count cards is not to calculate what the next card is, but a probability. Each suit has 13 cards, and the small cards are 2 to 6, so it is recorded as a positive one. The cards 7, 8 and 9 are zero. Big cards 10, j, q, k, a count as negative one. In the film, the hero won money only when he reached a very hot table. You will notice that his peers only give gestures when it is generally positive 15, 16 and 17, which means that the small cards are a lot from 2 to 6 (the sum of positive numbers is very high). Conversely, the probability of big cards will be high, so you will see that Waiting for 20 o'clock, when there are many big cards, it is not good for the dealer, because the dealer must make up the cards when he gets 16, and the chances of making up the big cards are high, and the chances of exploding (exceeding 2 1 point) are also high. The film is naturally exaggerated, but it is a real adaptation, which you can find online.